One of the most prevalent symptoms of childhood language impairment (LI) is word finding problems. Despite its prevalence, the underlying factor(s) responsible are as yet unclear. The long-term objectives of the proposed investigation are to clarify the nature of LI children's word finding deficits and identify the underlying source(s) of these disruptions. Recent on-line studies of word retrieval in other populations suggest that all aspects of the process may be candidates for perturbation. Further, individual differences in comprehension and production profiles may yield different patterns of disruption in the activation of processes engaged for word finding. The specific aims of this project are to examine four competing but not mutually exclusive hypotheses and determine the relative contribution of each to the word finding deficits of LI children: the storage-elaboration deficit, retrieval deficit, oral motor inefficiency and weak phonological representation hypotheses. The viability of these rival hypotheses will be tested by comparing the on-line naming performance of groups of gender and SES matched normal and LI children. Two groups of LI children: LI children with comprehension and production deficits and LI children with age level comprehension but deficient productive language who will be matched with one group of normal children for age and vocabulary comprehension. The first group of LI children will be matched with another group of normal children for language comprehension and production level; the second will be matched with another group of younger normal children for language production level. Each group will contain 80 subjects, 40 at each of two age levels, yielding a total sample size of 400 children. All subjects will participate in 4 on-line experiments which will examine their naming under two timing conditions while varying word frequency, the strength of associate primes, levels of phonological complexity and phonemic confusability of primes. Computer presentation of the tasks and on-line recording of responses as well as the use of new norms for vocabulary targets allow an unprecedented measure of stimulus manipulation and control that should make the underlying source(s) for LI children's word finding difficulties easier to identify.